| 摘要 |
A monitor for monitoring the performance of a digital transmission system has three level sensors for sensing at decision instants the level of a signal derived from a transmitted signal. A first of the level sensors has its threshold set at a level corresponding substantially to the eye diagram amplitude, a second has its threshold set near the upper level of the eye diagram amplitude, and the third has its threshold set near the lower level of the eye diagram amplitude. The outputs from the level sensors are connected to logic circuitry which is arranged to energize an alarm whenever the upper or lower eye amplitude level is between the thresholds of the second and third level sensors.
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